An electromechanical actuating unit of this general type is disclosed in international patent application WO 99/42739. The actuating element in the prior-art actuating unit is formed of the threaded nut of a screw actuator that is used as a reducing gear and has its threaded spindle driven by an electric motor. The anti-rotation mechanism of the threaded nut is provided by means of axial extensions inserted into semi-circular openings of a bearing plate. The bearing plate forms a bearing both for the threaded nut and the threaded spindle.
It is disadvantageous in the prior-art actuating unit that the mentioned anti-rotation mechanism of the actuating element is inappropriate for a modular design of the actuating unit or, respectively, that the reducing gear employed is untestable. Another shortcoming is the comparatively high cost of the unit, which is primarily due to the costly manufacture of the bearing plate and the threaded nut. Still another shortcoming is the risk that the axial extensions will jam in the bearing plate, in particular in the initial phase of the build-up of the clamping force, with the result of an impaired efficiency.